#include<stdio.h>
#include<stdlib.h>
#include<string.h>

char** A;
int elem=0;


struct nodo{

    char *s;
    struct nodo* sx;
    struct nodo* dx;

};

struct nodo* InsBin(struct nodo* t, char* w){

    if(t==NULL){
        struct nodo* new=(struct nodo*)malloc(sizeof(struct nodo));
        new->s=w;
        new->sx=NULL;
        new->dx=NULL;
        return new;
    }

    if ((strcmp(t->s,w))<0)
        t->dx=InsBin(t->dx,w);

    else t->sx=InsBin(t->sx,w);

return t;
}

struct nodo* cerca(struct nodo* t, char* w){

    if(t!=NULL){
        if(!(strcmp(t->s,w))) return t;
        else if((strcmp(t->s,w))<0)
            cerca(t->dx,w);
            else cerca(t->sx,w);
    }
    else return NULL;
}

void cpystring(struct nodo* t){

    if(t!=NULL){
        cpystring(t->sx);
        A[elem]=t->s;
        elem++;
        cpystring(t->dx);
    }
}

int main(){

    int n,i,l,ris,stop;
    char word[1000];
    char* temp;
    char* u;
    char* v;
    struct nodo* t=NULL;
    struct nodo* t1=NULL;
    scanf("%d",&n);
    A=(char**)malloc(n*sizeof(char*));
    for(i=0;i<n;i++) A[i]=NULL;
    elem=0;
    for(i=0;i<n;i++){
        scanf("%s",word);
        temp=(char*)malloc(1000*sizeof(char));
        strcpy(temp,word);
        t=InsBin(t,temp);
    }
    scanf("%s",word);
    t1=cerca(t,word);
    if(t1==NULL) ris=-1;
    else{
        cpystring(t1);
        if(A[1]==NULL) ris=strlen(A[0]);
        else{
            i=0;
            stop=0;
            while(i<n&&(!stop)){
                if(A[i]!=NULL)i++;
                else stop=1;
            }
            l=i;
            u=(char*)malloc(1000*sizeof(char));
            v=(char*)malloc(1000*sizeof(char));
            strcpy(u,A[0]);
            strcpy(v,A[l-1]);
            if(strlen(u)<=strlen(v))l=strlen(u);
                else l=strlen(v);
            i=0;
            while(i<l&&(u[i]==v[i]))
                    i++;
            ris=i;
        }
    }
    printf("%d\n",ris);
    return 0;
}